Golf ball with high specific gravity threads

ABSTRACT

A thread wound golf ball having improved characteristics of moment of inertia, spin, and total flight distance, comprising a center, a thread winding layer disposed over the center forming a core, and a cover disposed over the core. The improved characteristics are achieved by shifting the weight of the golf ball from the center towards the periphery by use of heavy thread. This could be achieved by adding a high specific gravity filler material, such as tungsten, to the conventional thread compound and/or using polymer materials in the thread that are inherently heavier. By using a high specific gravity filler material, other desirable characteristics inherent in a wound ball such as resilience, controllability and feel, are not affected.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates generally to compositions for golf balls.More specifically, the invention relates to an improved wound golf ballconstruction having high specific gravity thread windings so as toprovide increased moment of inertia and improved trajectory distance.

[0003] 2. Description of the Related Art

[0004] As is well known in the industry, there are a number of differenttypes of golf balls of which the predominant varieties are two-piece andthree-piece golf balls. A two-piece or solid golf ball typicallyconsists of a core and a cover. A three-piece ball typically consists ofa center, an intermediate layer, which may be solid or comprise one ormore elastomeric thread windings, and a cover. A ball with a solidintermediate layer is known as a multi-layered ball, while a ball withthread windings is referred to as a wound ball. In a three-piececonfiguration, the center and intermediate layer are collectively knownas the core. In the three-piece golf ball configurations, the center isusually made of natural or synthetic rubber and may be either solid orhave a liquid/paste form. The cover can be constructed from Balata,ionomer-based compounds, urethane compounds or any suitablethermoplastic or thermosetting material.

[0005] One of the parameters of golf ball performance that receivesgreat attention is flight distance. Although there are a variety offactors that influence a golf ball's flight distance, perhaps the mostimportant factors are the resilience characteristics and moment ofinertia of the ball, both of which are dictated in large part by thematerials used to construct the golf ball.

[0006] In general, solid golf balls have a higher moment of inertia incomparison to wound golf balls. This is due to the fact that theintermediate layer of a wound ball located between the center and coverhas the lowest specific gravity or density. This is attributed to thematerial used in the thread windings (typically polyisoprene rubber) andto the inherent voids formed between said windings when stretched andwound over the center. Golf balls with a higher moment of inertia willexhibit a lower spin rate at launch; also, the decay of spin duringflight is lower. Taken in combination, a lower spin rate at launch alongwith a decreased decay in that respective spin rate will increase theoverall distance that a golf ball can travel.

[0007] The resilience of a golf ball also affects the distance it willtravel, although not to the same degree as the moment of inertia. Hence,wound golf balls, which exhibit much higher resilience characteristicsin comparison to their solid counterparts, will not achieve the samedistance due to their lower moment of inertia. However, if the moment ofinertia of a wound ball is increased to that of a solid ball, the woundball would travel further than the solid ball due to the higherresilience of the wound ball. While a wound golf ball provides a golferwith better controllability and feel characteristics, it lacks a highmoment of inertia and thus is unable to provide the extra distance.

[0008] For the foregoing reasons, it is desirable to produce a woundgolf ball with a higher moment of inertia to improve the trajectorydistance that the ball travel, without affecting the wound ball'sinherent resilience, controllability and feel characteristics.

SUMMARY OF THE INVENTION

[0009] The present invention is directed towards a wound golf ball withan increased moment of inertia to improve the trajectory distance thatthe ball travels, without affecting the wound ball's inherentresilience, controllability and feel characteristics. A wound golf ballhaving features of the present invention comprises a center, the centerbeing either a solid rubber or fluid-filled center, an intermediatelayer comprising one or more elastomeric thread windings disposed overthe center forming a core, and an outer cover disposed over the corehaving a plurality of dimples. To increase the overall distance that theball will travel, the moment of inertia of the ball is increased byshifting the weight from the center towards the periphery of the ball.The weight shifting is accomplished by increasing the specific gravityof the thread to a value greater than 0.94, more particularly 0.96 andgreater, even more particularly 1.00 and greater, and still even moreparticularly 1.2 and greater. This is accomplished by (and notnecessarily in this order): (1) lowering the specific gravity of thecenter via the removal of the center's weight enhancing materials; and(2) by substituting conventional thread materials with materials havinga specific gravity value greater than 0.94, more particularly 0.96 andgreater, even more particularly 1.00 and greater, and still even moreparticularly 1.2 and greater and/or by adding high specific gravityfillers such as tungsten powder to the thread compound. By utilizing ahigh specific gravity material, desirable resilience and moduluscharacteristics inherent in a golf ball thread and windings are notcompromised.

BRIEF DESCRIPTION OF THE DRAWING

[0010] These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and the accompanying drawing which isgiven by way of illustration only, and thus is not limitative of thepresent invention and wherein:

[0011] The sole FIGURE of the drawing shows a cross section of a woundgolf ball according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0012] Referring to the drawing, attention is drawn to a wound golf ballcomprising a thread winding layer 1, which may be a thermoset orthermoplastic elastomer (TPE) formed of conventional materials known inthe art such as natural rubber and/or polyisoprene, other elastomerssuch as TPEs, polyurethane, latex etc., or any known material having aspecific gravity greater than 0.94, more particularly 0.96 and greater,even more particularly 1.00 and greater, and still even moreparticularly 1.2 and greater. This layer is disposed over a solid orliquid-filled center 3 forming a core 5. The core 5 is enshrouded by acover 7, which may be thermoplastic or a thermoset formed ofconventional materials known in the art such as Balata and/or syntheticrubber, ionomer resins, polyurethane, thermoplastic elastomers (TPEs) ora combination of the foregoing. The cover 7 is either a single ormulti-layered construction having a plurality of dimples (not shown) onits outermost surface. The center can be of two types, solid or liquid.The liquid center is one where liquid or gel is held in a rubber bag orshell that is well known in the art. The solid center is made from acombination of polybutadiene rubber, natural and/or polyisoprene rubber,zinc acrylate salt with weight enhancing materials and curatives. In apreferred embodiment, the center is made of a rubber compositioncomprising: 80-100 PPHR (parts per 100 parts by weight of the rubber inthe composition) of any polybutadiene, 0-20 PPHR of natural,polyisoprene or other synthetic rubber or thermoplastic, 10-30 PPHR ofzinc acrylate salt, 0-50 PPHR of weight enhancing materials (fillers),and 0.5-5 PPHR of curatives. The weight enhancing materials or fillersused are selected on the basis of specific gravity. In a preferredembodiment, the filler should have a specific gravity of about 4.3 orgreater. Zinc oxide, barium sulfate, tungsten etc., and their mixturesthereof are examples of suitable fillers.

[0013] The curatives used in forming the golf ball center can be any ofa variety of peroxides. The most important characteristic of theperoxide is its decomposition rate expressed by its half-life (t.sub.½).The half-life is the time required for one half of the molecules of agiven amount of peroxide (or its blend) at a certain temperature todecompose. The peroxide (or its blend) that would work in the presentsystem is one that has about a “one hour” half-life between 70 and 155°C. 1,1-Di-(tert-butylperoxy) -3,3,5-trimethyl-cyclohexane has a one-hourhalf-life between 105 and 115° C. Dialkyl peroxides, diacyl peroxides,peroxyesters and peroxyketals, alone or in combination, can be used asthe curing agent to produce a golf ball center having the desiredphysical properties. As set forth above,1,1-Di-(tert-butylperoxy)-3,3,5-trimethyl-cyclohexane, a peroxyketal, isthe preferred curing agent. Furthermore, a sulfur based cure system mayalso be employed (if necessary) to achieve the desired centerproperties. The sulfur based cure system is selected from the groupconsisting of elemental sulfur, chemical accelerators and blendsthereof.

[0014] The center is manufactured by using conventional compressionmolding processes. The components are mixed together in an internalmixer or any other suitable rubber mixing equipment and extruded to formpreforms if necessary, which are then placed in cavities in a mold andcompressed or transfer molded under pressure and temperature andcured/vulcanized to form centers. Preforms are necessary only if acompression molding technique is employed. The same mix may also beinjection molded. Curing is carried out in the mold at temperatures inthe approximate range of about 280-380° F. for 1-20 minutes depending onthe compound and the process used.

[0015] The thread winding layer 1 is formed of any suitable elastomerthread material, such as natural or polyisoprene or any syntheticthermoset rubber or TPE and their combinations thereof, that isstretched and wound about the center 3 as is conventional in the art.

[0016] To increase the flight distance of a conventional wound ball inaccordance with the present invention, the moment of inertia isincreased. Increasing the moment of inertia reduces the overall rate ofspin at launch and reduces the decay of spin during flight. Thisreduction in the spin rate and its corresponding decay, allows a golfball to travel further distances. In order to achieve a greater momentof inertia, the weight of the ball is shifted from the center of theball 3 to the thread winding layer 1. This is done by (and notnecessarily in this order): (1) reducing the amount of weight enhancingmaterials in the compound forming the center, which lowers the center's3 specific gravity; and (2) by incorporating a filler material having ahigh specific gravity (SG) in the approximate range of 5.6 or higher anda preferred SG of 19.3 (fine tungsten powder) into the thread and/or bysubstituting conventional thread materials with materials having aspecific gravity value greater than 0.94, more particularly 0.96 andgreater, even more particularly 1.00 and greater, and still even moreparticularly 1.2 and greater.

[0017] Filler materials having a high specific gravity are used in thethread or any material because they occupy the least volume in anycompound for a given weight and therefore, do not influence or reduceother desirable properties inherent in the wound golf ball such asresilience, controllability and feel. A listing of such inorganicelements or possible filler materials is provided in Table-1 below.

[0018] In one embodiment of the invention, threads incorporating suchhigh specific gravity filler materials are prepared by incorporatingsaid filler materials at the thread compound mixing or formulatingstages. This is then calendered or finished to the required dimensions.The weight percentage of tungsten in the thread compound ranges from0.1% to 30%, while in one embodiment, a weight percentage of 9.9% isnoted. The volume percentage of tungsten in the thread compound rangesfrom 0.1% to 10.0%, while in one embodiment, a volume percentage of 0.5%is noted. Hence, in the embodiment noted above, a compound formula of 11lbs of tungsten powder per 100 lbs of rubber is utilized. Once thecompound is produced, it is then cured and slit, as is normally done inthe conventional thread manufacturing process. Other suitable threadmanufacturing processes and/or materials may also be employed toincrease the specific gravity of the thread to a value greater than0.94, more particularly 0.96 and greater, even more particularly 1.00and greater, and still even more particularly 1.2 and greater. This maybe achieved by employing highly resilient polyurethane, TPEs or anyother known materials having a specific gravity of 0.94, moreparticularly 0.96 and greater, even more particularly 1.00 and greater,and still even more particularly 1.2 and greater (either with or withoutthe addition of high SG fillers), which would provide the functionalproperties necessary in its use and also the increased specific gravitythat would lead to an increased moment of inertia in the ball.

[0019] The dimension of the thread ranges from 0.008-0.028×0.015-0.125inch, while in one embodiment, the dimension of the thread isapproximately 0.017″×5/64 inch and has a specific gravity of about 0.95to 1.25, most particularly 1.04. This specific gravity can be higher orlower depending on the amount of tungsten filler added to the threadcompound and/or the non-filler thread material used. The specificgravity of the thread without the addition of weight enhancing materialsis about 0.94.

[0020] By adding high specific gravity fillers to the thread windinglayer 1 and/or by using materials with inherently higher (greater than0.94, more particularly 0.96 and greater, even more particularly 1.00and greater, and still even more particularly 1.2 and greater) SGvalues, the resulting golf balls produced can achieve an increasedmoment of inertia, which translates into increased ball performance,particularly in the areas of Driver Carry Distance and Driver Carry plusRoll Distance. Table-2 below provides calculated data for fourconventional golf ball constructions, and compares them to Ball #3,which represents a typical embodiment of the present invention wherebytungsten powder is incorporated in the thread compound of the threadwinding layer 1. The values given in Table-2 represent one embodiment ofthe invention (Ball #3); however, there are many conceivable variations(of Ball #3) as will be discussed below.

[0021] The center size of Ball #3 can range from 1.00-1.48 inches; thecenter weight of Ball #3 can range from 15-35 grams; the core size ofBall #3 can range from 1.48-1.68 inches; the core weight of Ball #3 canrange from 30-40 grams; the diameter of Ball #3 can range from 1.58-1.78inches; the weight of Ball #3 can range from 40-50 grams; the calculatedMoment of Inertia of Ball #3 can range from 12.4-13.4 (g-in²); theSpecific Gravity (SG) of the Center of Ball #3 can range from 1.2-1.3;the SG of the threads layer of Ball #3 can range from 0.7-1.25; the SGof the core of Ball #3 can range from 1.0-1.2; the thread layer weightof Ball #3 can range from 2.5-25.0 grams; and the thread layer thicknessof Ball #3 can range from 0.05-0.35 inches. With these parameters, aDriver Carry Distance of at least 258.16 yards and a Driver roll & CarryDistance of at least 277.68 yards is achieved.

[0022] It is to be understood that the present invention is by no meanslimited to the particular constructions herein disclosed and/or shown inthe drawing, but also comprises any modifications or equivalents withinthe spirit and scope of the claims. TABLE-1 Inorganic Element SpecificGravity Tungsten 19.3 Bismuth 9.8 Copper 8.9 Bismuth oxide 8.9 Nickel8.9 Cobalt 8.9 Iron/Steel 7.7 Tin 7.3 Chromium 7.2 Zinc 7.1 Bismuthsubcarbonate 6.9 Cupric oxide 6.4 Barium tungstate 6.4 Cuprous oxide 6.0Ferrous oxide 5.7 Zirconium dioxide 5.5

[0023] TABLE-2 Ball Data: Ball #1 Ball #2 Ball #3 Ball #4 Ball #5 Type3-piece 3-piece 3-piece 2-piece 2-piece Center Size 1.125 1.35 1.35 n/an/a ( in inches) Center Weight (g) 17.0 26.65 26.0 n/a n/a Core Size1.575 1.575 1.575 1.509 1.539 ( in inches) Core Weight (g) 35.65 35.6535.65 34.60 36.5 Ball Size 1.68 1.68 1.68 1.68 1.68 ( in inches) BallWeight (g) 45.5 45.5 45.5 45.5 45.5 Calculated Moment 12.43 12.45 12.5712.52 12.54 of Inertia (g-in²) Specific Gravity (SG) — 1.262 1.232 — —Of Center SG of Thread Layer — 0.725 0.777 — — SG of Core — 1.063 1.063— — Thread Layer — 9.00 9.65 — — Weight (g) Thread Layer — 0.1125 0.1125— — Size ( in inches) Flight Data: Driver Carry Distance — 254.64258.16 — — (yards) Driver Carry & — 272.63 277.68 — — Roll Distance

We claim:
 1. A golf ball comprising: a center; a thread winding layercomprising at least one thread, said thread having a specific gravitygreater than 0.94, and wherein said thread winding layer is disposedover said center creating a core; and a cover, wherein said cover isdisposed over said core.
 2. The golf ball of claim 1, wherein saidthread is comprised of a thermoset material having a specific gravitygreater than 0.94.
 3. The golf ball of claim 1, wherein said thread iscomprised of a thermoplastic elastomer (TPE) material having a specificgravity greater than 0.94.
 4. The golf ball of claim 1, wherein saidthread comprises at least one high specific gravity filler.
 5. The golfball of claim 2, wherein said thread further comprises at least one highspecific gravity filler.
 6. The golf ball of claim 3, wherein saidthread further comprises at least one high specific gravity filler. 7.The golf ball of claim 4, wherein said high specific gravity filler isselected from the group consisting of tungsten, bismuth, copper, bismuthoxide, nickel, cobalt, Iron/steel, tin, chromium, zinc, bismuthsubcarbonate, cupric oxide, barium tungstate, cuprous oxide, ferrousoxide and zirconium dioxide.
 8. The golf ball of claim 5, wherein saidhigh specific gravity filler is selected from the group consisting oftungsten, bismuth, copper, bismuth oxide, nickel, cobalt, Iron/steel,tin, chromium, zinc, bismuth subcarbonate, cupric oxide, bariumtungstate, cuprous oxide, ferrous oxide and zirconium dioxide.
 9. Thegolf ball of claim 6, wherein said high specific gravity filler isselected from the group consisting of tungsten, bismuth, copper, bismuthoxide, nickel, cobalt, Iron/steel, tin, chromium, zinc, bismuthsubcarbonate, cupric oxide, barium tungstate, cuprous oxide, ferrousoxide and zirconium dioxide.
 10. The golf ball of claim 4, wherein saidhigh specific gravity filler is tungsten.
 11. The golf ball of claim 5,wherein said high specific gravity filler is tungsten.
 12. The golf ballof claim 6, wherein said high specific gravity filler is tungsten.
 13. Amethod of making a thread winding layer having a high specific gravityfiller comprising the steps of: mixing a rubber and its components and ahigh specific gravity filler to form a mixture; calandering saidmixture; sheeting said mixture; curing said mixture; and slitting saidmixture into strips.
 14. The method according to claim 13, wherein saidhigh specific gravity filler is selected from the group consisting oftungsten, bismuth, copper, bismuth oxide, nickel, cobalt, Iron/steel,tin, chromium, zinc, bismuth subcarbonate, cupric oxide, bariumtungstate, cuprous oxide, ferrous oxide and zirconium dioxide.
 15. Themethod according to claim 13, wherein said high specific gravity filleris tungsten.
 16. A method of making a golf ball having high specificgravity threads comprising the steps of: mixing a rubber, curatives anda high specific gravity filler to form a mixture; calandering saidmixture; sheeting said mixture; curing said mixture; slitting saidmixture into strips to form at least one heavy thread; wrapping saidheavy thread around a center forming a core; and disposing a cover uponsaid core.
 17. The method according to claim 16, wherein said highspecific gravity filler is selected from the group consisting oftungsten, bismuth, copper, bismuth oxide, nickel, cobalt, Iron/steel,tin, chromium, zinc, bismuth subcarbonate, cupric oxide, bariumtungstate, cuprous oxide, ferrous oxide and zirconium dioxide.
 18. Themethod according to claim 16, wherein said high specific gravity filleris tungsten.
 19. A method of making a golf ball having high specificgravity threads comprising the steps of: wrapping at least one threadhaving a specific gravity greater than 0.94 around a center forming acore; and disposing a cover upon said core.
 20. The method of claim 19further comprising the step of adding a high specific gravity filler tosaid at least one thread.
 21. The method according to claim 20, whereinsaid high specific gravity filler is selected from the group consistingof tungsten, bismuth, copper, bismuth oxide, nickel, cobalt, Iron/steel,tin, chromium, zinc, bismuth subcarbonate, cupric oxide, bariumtungstate, cuprous oxide, ferrous oxide and zirconium dioxide.
 22. Themethod according to claim 20, wherein said high specific gravity filleris tungsten.